Medieval knighthood was physically grueling work: Jousting with massive lances. Charging into battle. Jogging on a treadmill in a full suit of armor. You know how it is.

It’s no surprise that beneath their shining armor, knights shimmered with sweat. Running around in up to 110 pounds of armor, or even advancing at a stately walk, would take a whole lot of effort. But, a team of scientists wondered, just how exhausting was it?

Since the researchers had missed their chance to track exertion on the jousting pitch by several hundred years, they recruited four modern volunteers, historical re-enactors from the Royal Armories in London. These guys had ample experience wearing armor, making them better proxies for knightly exertion than volunteers who wouldn’t know a culet from a cuirass. Each man donned a replica 15th-century suit of armor and hopped on a treadmill. As the volunteers walked and ran, the researchers kept tabs on their heart rate, their respiration rate, how much oxygen they used, and how long their strides were.

Sure enough, the researchers found, armor was exhausting. The men used 2.3 times as much energy to walk while wearing the armor than without it, and 1.9 times as much to run. Being outfitted for battle turned out to be even more tiring than hauling around a backpack of the same weight would’ve been. As it turns out, covering your legs with enormous, heavy metal plates makes moving around a lot harder.

What we’re really wondering is, how many extra lamb joints (or flagons of ale) would you have to consume per day to haul this carapace around? With accurate counts of energy spent wearing armor, one could perhaps gain insight into medieval knights’ calorie counts.